THERE are 2 teflon seals on the clutch drum support that "harden" & then leak for the 4th speed. Sounds as if this is your problem. Wish I could come over & find you a sutible repair shop.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V